Sulphur Dioxide

First of all, there is no such thing as Sulphur free wine. Sulphur is a basic element, naturally occurring in almost everything, including grapes and subsequently grape juice/wine.

In 2005 the European Union instated a law that demanded that all wines containing more than 10mg sulphur per litre, has to state “Contains sulphites” on the label. Which meant that all wines had to add this warning to their label, since they all naturally contain more than 10mg/litre. Most of which is derived from naturally occurring sulphur compounds created during the fermentation process.

Added sulphur is of course a different matter. Additions of sulphur dioxide is the norm within winemaking and has been for centuries. Sulphur dioxide is used as an antioxidant, antiseptic, anti-oxidasic and can also be used as a corrective after oxidation. In the beginning of the 20th century, before we fully understood the dangers of sulphur dioxide, it was not uncommon for dry wines to contain up to 500mg/l. But as winemaking improved, and winery hygiene procedures developed, our additions of sulphur dioxide have diminished. Today we have strictly regulated laws for how much total sulphur a wine may contain. They vary from country to country and between different types of wine (white and sweet wine needs more sulphur to keep them from reacting). But they are all within what is considered safe limits.

The Difference Between Free and Total Sulphur

When we talk about sulphur dioxide in wine, we are talking about total sulphur dioxide. Winemakers distinguish between free, bound, and total sulphur. Sulphur Dioxide is a reactive substance and when added to wine, part of it will react and change. This change is what protects the wine, for instance keeps it from oxidising, but this reaction also makes the used sulphur (known as bound sulphur) lose its protective properties, it is used up.

Depending on the wine’s quality, different amount of sulphur dioxide will be needed to saturate the wine, to make it stable. A poorly made wine or oxidised wine generally have higher proportions of aldehydes and ketones, which will bind with the added sulphur. What remains unbound afterwards is what winemakers call free sulphur. The free sulphur is what protects the wine during is further development.  The bound sulphur and free sulphur together add up to the total sulphur.  Too much free sulphur will affect the drinking experience of the wine, meaning that a wine maker will only add what is needed to ensure that the wine will not be damaged during its processing and ageing. A poor-quality wine will need more sulphur dioxide, while a healthy, well-made wine will survive on little.

Dangers of Sulphur Dioxide

Sulphur dioxide is undeniably toxic at high levels. It can be lethal, especially for people with pre-existing breathing difficulties, like asthma. Wine today contains very low levels of sulphur, levels that are deemed safe by the authorities. And while winemaking is only allowed to work with Sulphur dioxide (E220), Potassium metabisulphite (E224) and Potassium bisulphite (E228). Food producers are allowed to also work with Sodium metabisulphite and Sodium bisulphite. And while wine is strictly controlled and can in extreme cases contain a maximum of 350 ppm for dry wine (350g/l), foodstuff like dried fruit can contain up to 3500 PPM of sulphur dioxide (statistics from the US). Meaning that you consume far less sulphur dioxide drinking an entire bottle of mass-produced, American budget wine, then healthy kids do with dried fruit for lunch. And while wine is still allowed high levels of sulphur dioxide in certain countries, that upper level is rarely reached, and quality producers never even come close to it. If the viticulturalist has taken care and the winemaker knows what she is doing, the level of sulphur dioxide in dry wine should never be over 100mg/l, preferably even under 60mg/l.

Dangers of Not Adding Sulphur Dioxide

High levels of sulphur dioxide is undoubtedly bad, but so is also not adding it at all. Winemakers add sulphur dioxide for a reason, to keep the wine stable and safe. Even the highest quality wine, would be at risk to both oxidisation and microbial spoilage if low doses of sulphur dioxide were not added. While trendy natural wines tend to contain low levels of sulphur dioxide to ensure stability, some wines are produced with new, relatively untested alternatives. And while alternatives like glutathione, dimethyl dicarbonate, lysozyme, and chitosan looks promising as antioxidants, they simply do not have the range that sulphur dioxide has.

Something has to be added to ensure longevity and quality, and based on the knowledge we have today, low levels of sulphur dioxide is by far the safes alternative, and with the longest track record. That does not mean we will not find better alternatives in the future, but in the meantime, we simple have to accept that low levels of sulphur dioxide in our wine, offer the best results in regard to quality and longevity.

*Graph over allowed total Sulphur Dioxide in wine

 Dry RedDry White & RoséSparklingSemi-Sweet <50g sugar/lExtremely Sweet
Argentina130mg/l180mg/l 210mg/l 
Australia250mg/l250mg/l 300mg/l 
Canada (Ontario)300mg/l  400mg/l 
Chile250mg/l250mg/l 400mg/l 
New Zealand250mg/l  400mg/l 
South Africa150mg/l160mg/l 300mg/l 
EU Organic100mg/l150mg/l205mg/l220mg/l270mg/l